The Great Escape

Why it matters

Steam on the mirror, ice in the tray, the puddle that vanished — water tours all three states daily, and every switch happens at a temperature it refuses to negotiate.

The idea in plain words

The state-change dictionary. Tap the words.

melt · freeze · vaporise · condense · sublime

Why do naphthalene balls in a cupboard shrink and vanish without leaving a puddle?

No liquid stage — the solid escapes as gas

• pair 1: melting / freezing — solid ↔ liquid at the melting point (ice: 0 °C)
• pair 2: vaporisation / condensation — liquid ↔ gas (boiling point of water: 100 °C)
• the shortcuts: sublimation & deposition — solid → gas directly (camphor, naphthalene) and its reverse, gas → solid (frost forming) — no liquid stage either way
• They sublime: solid → vapour directly

Predict first

While ice is melting, the thermometer in the ice-water mix reads…

During a change of state, the heat goes into freeing molecules from each other — not into speeding them up. Temperature parks until the job is done.

• steady at 0 °C until all the ice is gone — correct
• slowly rising
• falling

What you do

Read the full heating curve of water — and explain what the flat parts are doing.

Check yourself

Steam turning to droplets on a cold mirror is…

Gas → liquid on the cold surface: vaporisation played backwards.

The temperature at which a solid melts is called its…

Pure ice melts at 0 °C, every time — so reliably that thermometers are calibrated on it.

Melting and freezing of water happen at…

One doorway, both directions: cross it downward and water freezes; upward and ice melts.

• condensation — correct
• evaporation
• sublimation
• melting point — fixed for a pure substance — correct
• boiling point
• freezing range — it varies day to day
• the same temperature: 0 °C — correct
• different temperatures
• 0 °C and 100 °C